With the rapid development of aquaculture and livestock and poultry farming, feed processing technology is also constantly improving. As an important equipment for modern feed production, feed extruders are widely used in fish feed, pet food, special breeding and other fields because they can process high-density, nutritionally balanced and easily digestible feed.
During the feed extrusion process, the nature of the raw materials has an important influence on the quality of the finished feed, especially the moisture content of the raw materials. The moisture content is not only related to the production efficiency and energy consumption of the extruder, but also directly affects the appearance, texture, floating and sinking properties and nutritional retention of feed particles.
This article will deeply analyze the requirements and precautions of the feed extruder for the moisture content of raw materials from multiple aspects, hoping to provide valuable reference for feed processing practitioners.
Before understanding the importance of moisture content, let's briefly understand the working principle of the feed extruder.
The feed extruder mainly uses spiral propulsion and heating to quickly gelatinize and mature the powdered or granular raw materials under high temperature, high pressure and high humidity, and extrude them at the die hole.
During the extrusion process, the raw materials are subjected to mechanical force, friction and shear force, the internal temperature rises sharply, and the water vaporizes quickly. When the raw materials are extruded from the die, the pressure is released instantly, and the water expands to form pores, which makes the feed have a certain degree of expansion and floating properties.
Since extrusion is a comprehensive process that integrates mixing, conveying, heating, gelatinization, dehydration and molding, the physical properties of the raw materials such as moisture, particle size, viscosity, etc. will affect the entire processing effect, among which the influence of moisture content is particularly prominent.
2.1 The influence of excessive moisture content
If the moisture content of raw materials is too high (generally more than 25%), the following problems will occur:
Difficult molding: the raw materials are too wet and cannot be fully heated and gelatinized, the feed particles are easy to loosen, the surface is rough or even broken;
Poor discharge: high moisture content increases the viscosity of the raw materials, and it is easy to adhere to the screw and the inner wall of the mold, causing blockage;
Poor puffing effect: too much moisture in the raw materials, the steam pressure is not enough to fully puff the feed, the particle density is large, and the buoyancy decreases;
Drying is difficult: the moisture content of the finished product is too high, the subsequent drying time is extended, and the energy consumption increases.
2.2 The influence of too low moisture content
If the moisture content of the raw materials is too low (less than 10%), it is also not conducive to extrusion molding:
Material transportation is difficult: the friction coefficient of the dried raw materials is large, and the transportation resistance increases;
Insufficient gelatinization: lack of sufficient moisture and high temperature, the degree of starch gelatinization is low, affecting the digestibility of the feed;
Fragile and fragile particles: insufficient puffing leads to loose feed structure, easy to break, and more powder.
Therefore, whether the moisture content is too high or too low, it will affect the processing quality and economic benefits of the feed. It is very important to find a reasonable moisture content range.
Different types of feed have slightly different requirements for the moisture content of raw materials. The common situations are as follows:
3.1 Fish feed
Fish feed usually requires particles to have good buoyancy or sinking properties. The moisture content of raw materials is usually controlled between 18% and 22%. The moisture content of floating feed can be slightly higher, and that of sinking feed can be slightly lower, so as to better control the particle density.
3.2 Pet feed
Pet feed requires good palatability and high swelling degree. The moisture content is usually controlled at 20% to 25% to ensure that the particles are uniform, fluffy, and beautiful in appearance.
3.3 Special feed (such as turtle and tortoise feed)
This type of feed requires hard particles and resistance to water immersion. The moisture content is generally controlled at 15% to 20% to ensure that the particles are compact and resistant to soaking.
It can be seen that different products can effectively improve the yield and stability of feed by adjusting the moisture content of raw materials according to needs.
In order to ensure the quality of feed extrusion, some measures need to be taken to control the moisture content of raw materials:
4.1 Raw material pretreatment
In the batching process, the moisture content of the main raw materials (such as corn flour, soybean meal, fish meal, etc.) should be tested. If the moisture content is too high, it can be reduced to the standard range through a dryer or natural drying.
4.2 Accurate water addition
Some raw materials are too dry, and water can be sprayed appropriately during mixing, but avoid excessive local humidity. Generally, high-precision humidification equipment is used to ensure uniform water addition.
4.3 Mixing evenly
Ensure that the raw materials are fully mixed after adding water to avoid local dryness and local wetness, which is very important for the consistency of the finished product.
4.4 Use a conditioner
Adding an appropriate amount of steam and water through the conditioner before extrusion to preheat and pre-cook the materials is conducive to improving the gelatinization and adhesion of the raw materials.
4.5 Monitoring moisture
Use a moisture meter to monitor the moisture content of the raw materials in real time to ensure that the process parameters can be adjusted at any time during the production process.
Reasonable moisture content needs to match other process parameters of the extruder, such as:
Temperature: When the moisture content is high, the temperature can be appropriately increased to help evaporation;
Screw speed: When the moisture content is high, the speed can be reduced to extend the material residence time;
Die hole diameter: Raw materials with high moisture content are adapted to larger die holes to avoid clogging.
The operator should flexibly adjust the parameters according to the characteristics of the raw materials and product requirements to find the best balance point.
In actual production, if the moisture content of the raw materials is not properly controlled, it often leads to a series of problems.
For example, when the moisture content of the raw materials is too high, the extruded feed particles will appear very soft and easy to break, and the drying time will be prolonged, affecting production efficiency. At this time, it is necessary to reduce the moisture content of the raw materials and extend the drying time to ensure the quality of the finished product.
If the moisture content of the raw materials is too low, it is easy to have serious particle powdering and insufficient puffing. In this case, water should be sprayed appropriately during mixing, and the steam volume should be reasonably adjusted to make the raw materials reach the appropriate moisture level.
In addition, if the moisture content of the raw materials is uneven or the overall moisture content is too high, it may also cause the die hole to be blocked and affect the discharge. At this time, it is necessary not only to appropriately reduce the moisture content of the raw materials, but also to ensure that the water addition process is uniform and fully mixed to avoid excessive local humidity.
Sometimes, the low puffing degree of feed pellets is also related to the unreasonable moisture content of the raw materials. Whether the moisture content is too high or too low, the puffing effect will be reduced. At this time, the moisture content should be adjusted to make the moisture content of the raw materials in the optimal range, and the extrusion temperature and pressure should be adjusted to obtain the ideal puffing effect.
In short, reasonable control of the moisture content of the raw materials is an important prerequisite for avoiding these problems and ensuring the quality of feed. For different abnormal situations, by scientifically adjusting the process parameters and moisture levels, the production stability and product quality can be effectively improved.
The feed extruder has key requirements for the moisture content of the raw materials, which should generally be controlled within a reasonable range of 15%~25%, and flexibly adjusted according to the characteristics of the specific products. Reasonable moisture content is not only conducive to the maturation, puffing and molding of raw materials, but also can improve production efficiency, reduce energy consumption, extend equipment life and improve feed quality. In actual production, enterprises should be equipped with professional testing equipment and process control methods, and through precise water addition, full mixing, conditioning and pretreatment, etc., the moisture content of raw materials is always in the best state, so as to produce high-quality feed products.
As a professional feed extruder seller, we are well aware of the importance of raw material moisture content to production, and have fully considered this factor in equipment design to help users more efficiently process high-quality feed that meets the requirements. We not only provide high-performance and easy-to-operate feed extruders, but also provide customers with complete technical support and process guidance to ensure that the equipment can achieve maximum efficiency.
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